Regulators shut down Houston-based Franklin Bank and Security Pacific Bank in Los Angeles on Friday, bringing the number of failures of federally insured banks this year to 19.

The Federal Deposit Insurance Corp. was appointed receiver of Franklin Bank, which had $5.1 billion in assets and $3.7 billion in deposits as of Sept. 30, and of Security Pacific Bank, with $561.1 million in assets and $450.1 million in deposits as of Oct. 17.

The co-founder and chairman of parent Franklin Bank Corp., Lewis Ranieri, is credited with inventing mortgage-backed securities two decades ago, but apparently was unable to save his own company from getting ensnared in the home-loan bust.

The bank's failure is a bitter irony because it is the mortgage securitization business of which Ranieri is known as a pioneer — the repackaging of home loans as bonds that are sold to investors — that was at the heart of the mortgage and credit crises. Last spring, the audit committee of the company's board found in an investigation certain weaknesses in accounting, disclosure and other issues relating to residential real estate loans.

Franklin Bank Corp. just Sunday said it had received proposals for transactions to strengthen Franklin Bank's capital position and was keeping regulators informed of the talks' progress.

The FDIC said all of Franklin Bank's deposits will be assumed by Prosperity Bank of El Campo, Texas. Its 46 offices will reopen as branches of Prosperity Bank with their normal business hours, including those that open on Saturday. In addition to assuming Franklin Bank's deposits, Prosperity Bank also will acquire about $850 million of the failed bank's assets.